Oil mist separators of this type are used in particular for the separation of oil mists and oil droplets from blow-by gases in an internal combustion engine. The blow-by gases are conventionally transported out of the crankcase by means of a ventilation line to the intake tract of the engine where they are recycled to the combustion process. However, it is necessary to first remove from the blow-by gases any oil that they may be carrying.
Depending on the operating conditions of the internal combustion engine, situations can thereby occur in which critical levels of operation are reached. On one hand, an excessive vacuum in the intake tract can cause the crankcase to be completely evacuated. An insufficient vacuum in the intake tract or an excessive pressure drop in the ventilation line can cause an overpressure to occur in the crankcase. However, an overpressure in the crankcase with respect to the atmospheric pressure cannot be allowed to occur.
Therefore, in the prior art, almost every internal combustion engine of the prior art includes pressure regulator valves in the blow-by path (ventilation line), which protect the crankcase from unallowably high vacuum. These valves close when the suction-side vacuum becomes too high and thereby cause an additional pressure drop in the blow-by line.
If only a low vacuum or an unallowably high pressure drop occurs in the intake line, for example on account of the clogging of one of the oil mist separators located in the intake line, bypass lines are provided in the ventilation line which bypass the corresponding locations, i.e. the oil mist separators. These bypass lines are closed by means of bypass valves which respond only when the pressure difference across a separator becomes too great. As a result of this bypassing, when the bypass valve is open, the vacuum of the intake tract of the engine is fully available in the crankcase for the ventilation of the crankcase. In this manner, an inflation of the crankcase is prevented.
DE 100 44 922 B4, for example, discloses a pressure regulator valve which is controlled by means of the pressure prevailing in the crankcase. The manipulated variable is thereby the pressure differential between the crankcase and the outside atmospheric pressure (constant pressure).
If the pressure in the crankcase increases, for example under operating conditions in which increased blow-by occurs, the pressure regulator valve opens again to effect an improved ventilation of the crankcase.
DE 20 2004 019 787 U1 describes an additional example of an oil mist separator in the blow-by ventilation line of an internal combustion engine. In this case a pressure regulator valve is located upstream of the oil mist separator. If the oil mist separator becomes clogged, there is a bypass line around the pressure regulator valve and the oil mist separator, which for its part is connected with a bypass valve. One problem with this example of the prior art is that the bypass valve is independent of the operating condition of the engine and the resulting intake vacuums. Therefore the bypass valve cannot react and adapt its response to different operating conditions.